1. Field of the Invention
This invention relates to an audible sound which is able to induce Fm theta in human brain waves, as well as to a method, device and recorded medium to generate the same.
2. Description of the Prior Art
Potential differences observed two different sites in the cerebral cortex and scalp are called as "brain waves" which have characteristic waveforms and rhythms correspondently to mental and physical conditions. Brain waves are usually classified into four types, i.e. "alpha wave", "beta wave", theta wave and "delta wave" based on their frequencies. Among these, alpha wave, which usually lies in the frequency range of 8-13 hertz, strongly, extensively and continuously appears as mind and body relax. While beta wave, which usually lies in the frequency range of 18-30 hertz, strongly and extensively appears as mind and body contract. Theta and delta waves, which are 4-8 hertz or less than 4 hertz respectively, are relevant to hypnosis and sleep: It is said that theta wave strongly appears in hypnagogic stage, while delta wave in turn becomes predominant as sleep becomes deeper. As seen in Inoeu et al., The EEG of Mental Activities, pp.136-148 (1988), certain theta wave which is observed as predominant rhythm of 6-7 hertz around the frontal midline in adult is called as "Fm theta" and said to be closely relevant to mental tasks. One can observe Fm theta appearing around the frontal midline in persons who are in mental tasks, and its magnitude and distribution become strong and extensive as the persons' attention and concentration increase.
Since as described above Fm theta is closely connected with attention and concentration, if Fm theta is artificially induced in workers, then it is expected to improve their attention and concentration as well as to improve efficiency and accuracy of tasks. There have been however available no devices and processes which can be used to artificially induce Fm theta.